On
14 October 2011, scientists flying over Antarctica’s Pine Island
Glacier (PIG) ice shelf as part of NASA’s Operation IceBridge
mission made a startling discovery: there was a massive rift running
about 29 kilometers (18 miles) across a part of the glacier’s
floating tongue. The rift was 80 meters (260 feet) wide on average,
and 50 to 60 meters (170 to 200 feet) deep.

When
the crack reaches the other side of the ice shelf, it will send a
huge new iceberg drifting into Pine Island Bay. Since discovering it,
researchers have monitored the rift closely with remote sensing
equipment. This pair of images, acquired by a synthetic aperture
radar on Germany’s TerraSar-X satellite, shows how it lengthened
and widened between 31 October 2011, and 14 September 2012. In May
2012, a second crack formed west of the original one. Download the
animation to see how this part of the ice shelf and the rift has
changed since May 2011.

Rifts
similar to this form on the Pine Island Glacier’s ice shelf every
five-to-six years. “What makes this one remarkable is that it will
lead to calving of a significantly larger iceberg than PIG has
produced in the last few decades,” noted Joseph MacGregor, a
research scientist at the University of Texas at Austin. “It is
likely that the front of PIG will be farther back than any time in
the recent past after the iceberg calves,” he said.

Satellites
observed large icebergs calving off Pine Island Glacier in 2001 and
2007, but upcoming IceBridge flights offer an opportunity to monitor
a calving event from closer range. Operation IceBridge resumed
science flights with NASA’s DC-8 on 12 October 2012. Scientists
participating in the mission will be watching the crack closely for
any new signs of change.